syzbot

ext4 filesystem being mounted at /50/bus supports timestamps until 2038-01-19 (0x7fffffff)
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.67/4553 is trying to acquire lock:
ffff88807079dca8 (&dquot->dq_lock){+.+.}-{3:3}, at: dquot_commit+0x5a/0x410 fs/quota/dquot.c:507

but task is already holding lock:
ffff88805dbb8288 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_map_blocks+0x910/0x1b70 fs/ext4/inode.c:672

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&ei->i_data_sem/2){++++}-{3:3}:
       down_read+0x42/0x2d0 kernel/locking/rwsem.c:1520
       ext4_map_blocks+0x323/0x1b70 fs/ext4/inode.c:604
       ext4_getblk+0x1cc/0x6f0 fs/ext4/inode.c:890
       ext4_bread+0x26/0x170 fs/ext4/inode.c:946
       ext4_quota_write+0x236/0x580 fs/ext4/super.c:7222
       write_blk fs/quota/quota_tree.c:70 [inline]
       get_free_dqblk+0x312/0x660 fs/quota/quota_tree.c:136
       do_insert_tree+0x22b/0x1040 fs/quota/quota_tree.c:347
       do_insert_tree+0x9eb/0x1040 fs/quota/quota_tree.c:402
       do_insert_tree+0x9ae/0x1040 fs/quota/quota_tree.c:402
       do_insert_tree+0x9ae/0x1040 fs/quota/quota_tree.c:402
       dq_insert_tree fs/quota/quota_tree.c:432 [inline]
       qtree_write_dquot+0x49d/0x5d0 fs/quota/quota_tree.c:451
       v2_write_dquot+0x108/0x190 fs/quota/quota_v2.c:361
       dquot_acquire+0x2d5/0x520 fs/quota/dquot.c:472
       ext4_acquire_dquot+0x2d9/0x4a0 fs/ext4/super.c:6831
       dqget+0x778/0xeb0 fs/quota/dquot.c:988
       dquot_transfer+0x37c/0x7e0 fs/quota/dquot.c:2150
       ext4_setattr+0x93d/0x19f0 fs/ext4/inode.c:5520
       notify_change+0xc74/0xf40 fs/attr.c:499
       chown_common+0x4a0/0x660 fs/open.c:736
       do_fchownat+0x147/0x240 fs/open.c:767
       __do_sys_chown fs/open.c:787 [inline]
       __se_sys_chown fs/open.c:785 [inline]
       __x64_sys_chown+0x7e/0x90 fs/open.c:785
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&s->s_dquot.dqio_sem){++++}-{3:3}:
       down_read+0x42/0x2d0 kernel/locking/rwsem.c:1520
       v2_read_dquot+0x4a/0x110 fs/quota/quota_v2.c:335
       dquot_acquire+0x152/0x520 fs/quota/dquot.c:463
       ext4_acquire_dquot+0x2d9/0x4a0 fs/ext4/super.c:6831
       dqget+0x778/0xeb0 fs/quota/dquot.c:988
       __dquot_initialize+0x3c3/0xcd0 fs/quota/dquot.c:1517
       ext4_process_orphan+0x54/0x300 fs/ext4/orphan.c:327
       ext4_orphan_cleanup+0xbeb/0x1420 fs/ext4/orphan.c:472
       __ext4_fill_super fs/ext4/super.c:5556 [inline]
       ext4_fill_super+0x7829/0x7dc0 fs/ext4/super.c:5687
       get_tree_bdev+0x3f1/0x610 fs/super.c:1366
       vfs_get_tree+0x88/0x270 fs/super.c:1573
       do_new_mount+0x24a/0xa40 fs/namespace.c:3078
       do_mount fs/namespace.c:3421 [inline]
       __do_sys_mount fs/namespace.c:3629 [inline]
       __se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3606
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&dquot->dq_lock){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3090 [inline]
       check_prevs_add kernel/locking/lockdep.c:3209 [inline]
       validate_chain kernel/locking/lockdep.c:3825 [inline]
       __lock_acquire+0x2d07/0x7d10 kernel/locking/lockdep.c:5049
       lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12d/0xaf0 kernel/locking/mutex.c:747
       dquot_commit+0x5a/0x410 fs/quota/dquot.c:507
       ext4_write_dquot+0x1f0/0x360 fs/ext4/super.c:6811
       mark_dquot_dirty fs/quota/dquot.c:372 [inline]
       mark_all_dquot_dirty+0xf9/0x400 fs/quota/dquot.c:412
       __dquot_alloc_space+0x5fc/0xe60 fs/quota/dquot.c:1752
       dquot_alloc_space_nodirty include/linux/quotaops.h:300 [inline]
       dquot_alloc_space include/linux/quotaops.h:313 [inline]
       dquot_alloc_block include/linux/quotaops.h:337 [inline]
       ext4_mb_new_blocks+0xf8d/0x4760 fs/ext4/mballoc.c:5738
       ext4_ext_map_blocks+0x195b/0x6810 fs/ext4/extents.c:4340
       ext4_map_blocks+0x9de/0x1b70 fs/ext4/inode.c:679
       ext4_getblk+0x1cc/0x6f0 fs/ext4/inode.c:890
       ext4_bread+0x26/0x170 fs/ext4/inode.c:946
       ext4_append+0x2be/0x560 fs/ext4/namei.c:83
       ext4_init_new_dir+0x2b8/0x570 fs/ext4/namei.c:3030
       ext4_mkdir+0x4fb/0xce0 fs/ext4/namei.c:3076
       vfs_mkdir+0x387/0x570 fs/namei.c:4114
       do_mkdirat+0x1d8/0x440 fs/namei.c:4139
       __do_sys_mkdirat fs/namei.c:4154 [inline]
       __se_sys_mkdirat fs/namei.c:4152 [inline]
       __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4152
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Chain exists of:
  &dquot->dq_lock --> &s->s_dquot.dqio_sem --> &ei->i_data_sem/2

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ei->i_data_sem/2);
                               lock(&s->s_dquot.dqio_sem);
                               lock(&ei->i_data_sem/2);
  lock(&dquot->dq_lock);

 *** DEADLOCK ***

4 locks held by syz.0.67/4553:
 #0: ffff88807bd6c460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:402
 #1: ffff88805d97d440 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:793 [inline]
 #1: ffff88805d97d440 (&type->i_mutex_dir_key#3/1){+.+.}-{3:3}, at: filename_create+0x208/0x470 fs/namei.c:3884
 #2: ffff88805dbb8288 (&ei->i_data_sem/2){++++}-{3:3}, at: ext4_map_blocks+0x910/0x1b70 fs/ext4/inode.c:672
 #3: ffffffff8cc74a48 (dquot_srcu){....}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #3: ffffffff8cc74a48 (dquot_srcu){....}-{0:0}, at: srcu_read_lock include/linux/srcu.h:165 [inline]
 #3: ffffffff8cc74a48 (dquot_srcu){....}-{0:0}, at: __dquot_alloc_space+0x173/0xe60 fs/quota/dquot.c:1716

stack backtrace:
CPU: 1 PID: 4553 Comm: syz.0.67 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3090 [inline]
 check_prevs_add kernel/locking/lockdep.c:3209 [inline]
 validate_chain kernel/locking/lockdep.c:3825 [inline]
 __lock_acquire+0x2d07/0x7d10 kernel/locking/lockdep.c:5049
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5662
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x12d/0xaf0 kernel/locking/mutex.c:747
 dquot_commit+0x5a/0x410 fs/quota/dquot.c:507
 ext4_write_dquot+0x1f0/0x360 fs/ext4/super.c:6811
 mark_dquot_dirty fs/quota/dquot.c:372 [inline]
 mark_all_dquot_dirty+0xf9/0x400 fs/quota/dquot.c:412
 __dquot_alloc_space+0x5fc/0xe60 fs/quota/dquot.c:1752
 dquot_alloc_space_nodirty include/linux/quotaops.h:300 [inline]
 dquot_alloc_space include/linux/quotaops.h:313 [inline]
 dquot_alloc_block include/linux/quotaops.h:337 [inline]
 ext4_mb_new_blocks+0xf8d/0x4760 fs/ext4/mballoc.c:5738
 ext4_ext_map_blocks+0x195b/0x6810 fs/ext4/extents.c:4340
 ext4_map_blocks+0x9de/0x1b70 fs/ext4/inode.c:679
 ext4_getblk+0x1cc/0x6f0 fs/ext4/inode.c:890
 ext4_bread+0x26/0x170 fs/ext4/inode.c:946
 ext4_append+0x2be/0x560 fs/ext4/namei.c:83
 ext4_init_new_dir+0x2b8/0x570 fs/ext4/namei.c:3030
 ext4_mkdir+0x4fb/0xce0 fs/ext4/namei.c:3076
 vfs_mkdir+0x387/0x570 fs/namei.c:4114
 do_mkdirat+0x1d8/0x440 fs/namei.c:4139
 __do_sys_mkdirat fs/namei.c:4154 [inline]
 __se_sys_mkdirat fs/namei.c:4152 [inline]
 __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4152
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f34d559b607
Code: 00 66 90 48 89 f2 b9 00 01 00 00 48 89 fe bf 9c ff ff ff e9 db f7 ff ff 66 2e 0f 1f 84 00 00 00 00 00 90 b8 02 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe05afb9a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007ffe05afba30 RCX: 00007f34d559b607
RDX: 00000000000001ff RSI: 00002000000016c0 RDI: 00000000ffffff9c
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00002000000016c0
R13: 00007ffe05afb9f0 R14: 0000000000000000 R15: 0000000000000000
 </TASK>